Question

Consider the following 8051 interfacing problem. Crystal frequency: 11.059MHz. The LED  

D8 will light up with every key press as shown below.

45V HE C3 1DF R2 Sk U1 R10 40 VCC >XTALI LED-YELLOW XTAL2 12MHz DB REAL Hoh RST CRYSTAL PODADO PO WAD1 PO 2 AD2 POSIAD) PO4AD4 POVADS PO GADS PO ZADT P20:48 P2149 P22A10 P23A11 P24A12 P2513 P28A14 P2TAS 21 C1 C2 R9 102 RA PSEN ALE EA P10 P11 P12 P13 P14 P3 ORXD P31/TXD P3.2 INTO PINTI 934 TO 73.5T1 P36WR 1 1 P15 P16 P1 ATEBC51 375 GND 20

1. Initialize IE register for external interrupt at INT0

2. Initialize TCON register for the appropriate type of interrupt

3. Declare and define the interrupt service routine

4. Access and configure relevant pin as needed

5. Call back action in the main function as needed

Answer 1

(i) Interrupt Enable (IE) register. It is used to enable con disable Various available interrupts 167 TE•G DES LE.4 IE3 IE.2 IEI LEO EA ETRES ET EXi Eto Exo , EAT Enable any of the interrupts 1- Enable o-disable ET₂ - Timera enable bit Es - serial port interrupt enable ETI Timert interrupt enable o-disable EXI > External interrupt INT, enable ETO → Timero interrupt enable Exot External interrupt INTo enable To enable l-enable INTO o 0 0 8 IH IE li TCON ITO (Timer control resister) TONI TONOO TONA TCONG ITFITRI TFO | TROIE, ITTED Ito > enable external interrupto to be triggered by falling edge (edge triggered) ITO =0 - enable low level triggered IT, enable edge triggered CINTI) 'ITRO enable Low level triggered TRO,TFO → Timero Run & overflow flag respectively TRTFI → Timer 1 Rank overflow flag to make INTO as falling edge triggered set TCONGO → logict

ii) Interrupt service routine (ISR) = when the interrupt is enabled, control is transfered to ISR & code in the ISR will be executed since 22.0 + LED is ISR ; MOV A, #ool connected Μον Ρ1, Η as cathode of LED is RET Connected to pzoo turn ON LED can be done by making p2:0=0') iv, program: [rector address of INTO interrupt is 0003.) ORG 0001 SJMP MAIN ORG 003H ACALL ISR RET I MAIN: MOV IE, #817 SETB TCON.C SETR Ipoo V. (to enable Into interrupt) ( to make falling edge triggered) ( to make Into has high prianity) SJMP MAIN ISRO MOV A, #0014 MOV P2, A RET

Thank You....!!!!
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